A wild bonobo has been seen cannibalising her own recently deceased two and a half-year-old infant.

Among apes, such behaviour is extremely rare, only being reported before among orangutans, and never by bonobos, our closest relative alongside chimps.

Though uncommon, the behaviour may not be aberrant, says the scientist who witnessed it.

But it does further challenge a widely perceived notion that bonobos are an especially "peaceful" ape species.

The discovery is reported in the American Journal of Primatology.

Bonobos (Pan paniscus) were once known as pygmy chimps, due to their similarities with the common chimpanzee (Pan troglodytes), from which they diverged in the past one million years.

Researchers have often emphasised the differences in behaviour between the two species; bonobos are reported as being less aggressive, hostile to one another, and living in societies dominated by females rather than high-ranking males that control communities of common chimps.

The idea of the 'Hippy Chimp' is more a metaphor than a scientific argument

Dr Andrew FowlerMax Planck Institute for Evolutionary Anthropology

They were also regarded as less violent, being thought not to commit infanticide or hunt and eat other primate species.

Last year, however, that more peaceful image was shattered when scientists discovered that bonobos do kill and eat monkeys.

Now, primatologists Dr Andrew Fowler and Dr Gottfried Hohmann of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany have recorded an example of a bonobo ape consuming, along with other apes in her group, the body of her recently deceased infant.

Taking of the body

Dr Fowler and colleague Ms Caroline Deimel were conducting routine observations of a group of bonobos living in the forest at Lui Kotale in the Democratic Republic of Congo.

Through the trees, they saw a female called Olga carrying her dead infant, Olivia, over her shoulder.

That morning Olivia had been seen alive, and her body showed no signs of injury.

The next day, Olga still carried her dead infant, and spent an hour or so grooming her body.

"After an hour, Marta, a dominant female then took the body, retaining it despite initial resistance from Olga. She then began to consume it, joined by most of the community including the mother," Dr Fowler told the BBC.

"Consumption took several hours, and possession of the carcass changed several times. At times Olga and Ophelia, her remaining daughter, were not involved but remained nearby throughout the period," he says.

"When a single foot and hand only remained attached to a long skin fragment, Olga took the remains, placed them over her back and walked away."

Dr Fowler says that such behaviour is not usual, but it may be more widespread than this one incident.

Researchers may have witnessed it, but been unwilling to report it for fear of drawing undue attention to cannibalism among our close relatives, he says.

Or there may simply not have been enough long-term studies of bonobos to previously notice it.

Infanticide, the practice of killing younger members of the same species, occurs among common chimps and gorillas.

Cannibalism, where animals eat their own kind, has also been reported among chimps, and inferred on one ocassion in gorillas.

Biologists believe that infanticide is often triggered by males who wish to eliminate infants carrying genes different to their own.

I don't think it necessarily says anything about 'empathy' or 'morality'

Dr Andrew FowlerMax Planck Institute for Evolutionary Anthropology

By killing infants, they can also make the mothers sexually receptive again, increasing their own chances or mating with her.

Filial cannibalism, where a mother eats her own offspring, is much rarer, particularly among great apes, in which it has only once been reported before.

Last year, Mr David Dellatore of Oxford Brookes University in the UK reported two incidences of female orangutans eating their recently deceased babies.

He suspected the orangutans may have acted this way due to stress.

But Dr Fowler believes the behaviour may occur among apes more often.

Like Mr Dellatore, Dr Fowler is reluctant to make any definitive claims as to why the behaviour occurred.

He suspects that Olga and the other bonobos consumed Olivia's body for nutritional gain, even though it carried a risk of contracting disease from the dead infant.

Sexy and peaceful?

However, says Dr Fowler: "I am not sure there are wider implications from a scientific point of view."

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